1. Field of the Invention
The present invention relates to a non-aqueous electrolyte battery. More particularly, the present invention relates to a non-aqueous electrolyte battery that can be used as a lithium ion battery capable of reversely exchanging lithium ions between positive and negative electrodes.
2. Description of the Related Art
Since an electrolyte battery has excellent characteristics such as light weight, high energy density and less self-discharge, the electrolyte battery has intensively studied and developed, recently.
Particularly in the case of a lithium ion secondary battery in which a charge-discharge reaction proceeds by repeating dedoping and doping of lithium ions with which a negative electrode active material or a positive electrode active material has been chemically and physically doped in advance, large energy density is obtained compared with a lead battery and a nickel cadmium battery that are other non-aqueous electrolyte batteries. Therefore, demands for the lithium ion secondary battery as a power supply to be mounted in a portable electronic equipment such as a mobile phone have been increased. With further miniaturization and weight saving of the portable electronic equipment, further miniaturization and an increase in energy density are required to the non-aqueous electrolyte battery as a power supply.
In order to reduce carbon dioxide to be discharged from a vehicle as a dispersion type emission source of carbon dioxide that is said to be a cause of global warming, it is required to put a hybrid vehicle and an electric vehicle into practical use. A development of a lithium ion secondary battery having high weight energy density and volume energy density holds a key to this practical use. In order to establish a sustainable society, it is indispensable to increase a use rate of natural energy among energy to be supplied, and a solar battery has commonly become popular as one of supply sources of natural energy. Herein, a lithium ion secondary battery is also considered as a useful member capable of storing electricity generated by a solar battery in view of energy density and capacity. As described above, the lithium ion secondary battery exerts an influence on the development in various fields.
Commonly, the lithium ion secondary battery is comprised of a negative electrode, a positive electrode, a separator, an electrolyte or an electrolytic solution, and a battery container that accommodates them. Examples of the electrolytic solution to be used in the lithium ion secondary battery include those prepared by dissolving LiPF6, LiBF4, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2) (C4F9SO2), LiC(CF3SO2)3, LiC(C2F5SO2)3, LiAsF6, LiClO4, Li2B10Cl10, Li2B12Cl12 and mixtures thereof, as electrolyte salts, in a carbonic acid ester-based non-aqueous solvent such as ethylene carbonate, propylene carbonate or diethyl carbonate.
The electrolytic solution containing LiPF6 dissolved therein is widely used in view of solubility in an organic solvent and high electric conductivity, but has such a problem that it is inferior in thermostability and storage characteristics. The electrolytic solution containing LiBF4 dissolved therein shows high thermostability and oxidation stability, but has such a problem that it is inferior in electric conductivity. Furthermore, the electrolytic solution containing LiCF3SO3 dissolved therein shows high thermostability, but has such a problem that it is inferior in electric conductivity and oxidation stability, and that sufficient discharge characteristics cannot be obtained when charged at a high voltage of 4 V or more. Furthermore, an electrolytic solution containing LiN(CF3SO2)2, LiClO4 or LiAsF6 dissolved therein shows high electric conductivity, but has such a problem that it is inferior in cycle characteristics. Furthermore, an electrolytic solution containing LiN(C2F5SO2)2 or LiN(C4F9SO2) (CF3SO2) dissolved therein shows high electric conductivity and also has excellent thermostability but is inferior in oxidation stability, thus causing a problem that sufficient cycle characteristics cannot be obtained when charged and discharged at a high voltage of 4 V or more.
As described above, conventional electrolytic solutions containing electrolyte salts dissolved therein could not simultaneously satisfy cycle characteristics and storage stability while maintaining excellent electric conductivity. Lithium fluoride LiF and hydrogen fluoride HF to be produced by thermolysis or hydrolysis of a lithium salt in the electrolytic solution are considered as a cause for deterioration of battery performances such as cycle characteristics and storage stability. Therefore, there has been required a technique that sufficiently suppresses an influence of hydrogen fluoride at high temperature. There has also been required a technique that sufficiently suppresses an influence of hydrogen fluoride over a long period.
In order to respond to these requirements, Japanese Unexamined Patent Publication No. 2001-93571 (Patent Document 1) describes a technique in which a 1,8-bis(dialkylamino)naphthalene derivative such as 1,8-bis(dimethylamino)naphthalene is added to the electrolytic solution so as to impart cycle characteristics and storage stability at high temperature.
Also, Japanese Unexamined Patent Publication No. HEI 7(1995)-211349 (Patent Document 2) describes a method in which an adsorbent of a metal oxide such as aluminum oxide is built in the battery and adsorption removal is conducted.
Also, Japanese Unexamined Patent Publication No. HEI 4(1992)-355057 (Patent Document 3) describes a method in which adsorption removal is conducted using activated carbon or silica gel.
Also, Japanese Unexamined Patent Publication No. HEI 3(1991)-119667 (Patent Document 4) describes a method in which a basic treating agent such as an ammonium salt is used.
Also, Japanese Unexamined Patent Publication No. HEI 1(1989)-286262 (Patent Document 5) describes a method in which an organic lithium compound such as pentafluorophenyl lithium is added to the electrolytic solution.
Also, Japanese Unexamined Patent Publication No. 2001-506052 (Patent Document 6) proposes a technique in which a decomposition reaction caused by an acid is suppressed by neutralizing an acid generated in the battery. Specifically, the document describes a technique in which a basic compound such as a metal-containing base, a carbonate, a metal oxide, a hydroxide, an amine or an organic base is added to the electrolytic solution.